In recent years, because the economical, industrial and business prosperity people's livelihood has been greatly promoted, and taxi-cabs and private cars become so popular. During winter time, if the windows of a vehicle is tightly closed, not only the windshield and windows of a vehicle will become foggy which blocks out driver's sight, but also the air in the passenger compartment of a vehicle will gradually become dirty, the worst of it is the passengers smoke in the passenger compartment, if for the ventilation purpose some windows of the vehicle are partly opened, cold wind and some times with rain drops will blow into the passenger compartment which disturbes both driver and passengers and may even cause them sick.